Various devices are known for forming stacks of banknotes. One such device is described in published European patent application No. 0684929. This discloses an apparatus which incorporates a pusher plate with which a banknote may be pushed from the plane along which the banknote is transported to the stacking mechanism (transport plane), into a cashbox situated adjacent to the banknote plane. The pusher plate is connected by a pivoted lever arrangement via a cam, to a drive motor. The pivoted lever arrangement operates with a “scissors action” to cause the pusher plate to push the banknote into the cashbox against the action of a spring mounted stack surface. The banknotes are retained in a stack in the cashbox, when the pusher plate is withdrawn, by flanges which abut the ends of the uppermost surface of the banknote stack.
Other stackers with a vertical scissors arrangement driving a pusher are disclosed in U.S. Pat. No. 4,807,736, EP 0751487, U.S. Pat. No. 4,809,966, U.S. Pat. No. 5,344,135, U.S. Pat. No. 5,421,443, U.S. Pat. No. 4,765,607, U.S. Pat. No. 5,419,423, and U.S. Pat. No. 4,784,274.
Although this type of arrangement provides an efficient method of stacking banknotes, the required depth of stroke of the pusher plate is linked to the size of the aperture through which the banknote is pushed. Thus, a short depth of stroke is only possible if the aperture is relatively large. However, cashboxes with relatively large apertures suffer from the disadvantage of being difficult to make secure (i.e. self closing) on detachment from the stacking device. Also, where the cashbox is used with multiple denominations of notes (having different widths), the aperture must be significantly shorter than the width of the shortest banknote to be stacked. This is in order that the flanges at the ends of the aperture may retain even the shortest banknotes. This results in a minimum length of pusher plate stroke being further increased in order to successfully stack the widest banknotes through the same aperture size and hence a corresponding increase in the depth of the cashbox.
The cashbox aperture may be made smaller by increasing the depth of stroke of the pusher plate. However, an increased depth of stroke results in an increased cashbox depth for any given size of banknote stack. As space is often at a premium in such circumstances, for example in combined banknote validator and stacker devices, this too is an undesirable consequence.
U.S. Pat. No. 4,809,967 and U.S. Pat. No. 5,014,857 disclose a stacking device of the piston type which aims to address the problem of ensuring that banknotes flatten correctly on the stack surface during the stacking process. These disclosures teach to incorporate pivotally mounted “unfolding” plates in the piston assembly. These are arranged to displace horizontally as the piston stroke increases in the vertical direction; thus assisting in flattening a banknote against the stack.
However despite assisting with flattening banknotes in the stacking procedure the device of U.S. Pat. No. 4,809,967 and U.S. Pat. No. 5,014,857 suffers from the same drawback as that of EP 0684929A, in that a short depth if stroke is only possible of the cashbox aperture is relatively large; or, conversely a small aperture is only achievable if the stroke length is relatively long.
U.S. Pat. No. 6,244,589 shows a stacker which is arranged to stack through a relatively narrow aperture (thus providing enhanced security) with a relatively short stroke (thus making efficient use of cashbox volume), using, in one embodiment, a pair of rotor arms.